I've always used thumb grips with the X100F (T,S,0) since it improves the grip tremendously. When I use the hotshoe however, the grip must be removed and once again I return to a hard to grip camera. When I was in Japan, I bought a sheet of camera leather tape in a hobby store. I didn't think much of it then but it became useful very quickly as I started using it on many parts of the camera.
I've found a great grip for the X100T. As an alternative to leather half cases and other grips, it retains a small profile. It is unobtrusive, grippy and best of all it is made from a natural material.
For a long time I've used the Gariz Leather case to improve grip, though I've always had some issues with the leather case making the camera too thick. Enter the Rosewood grip.